Risk factors for optic nerve disease in communities mesoendemic for savannah onchocerciasis, Kaduna State, Nigeria

Abstract

SummaryOphthalmic examinations on 6831 individuals aged 5 years or more, living in 34 guinea savannah communities mesoendemic for onchocerciasis, in Kaduna State, Nigeria, revealed a relatively high prevalence (9%) of optic nerve disease (OND). Further investigations were performed to determine what proportion of this burden of OND might be due to onchocercal infection. Information on history of cerebro-spinal meningitis (CSM), past use of diethylcarbamazine (DEC) and chloroquine, consumption of cassava and locally produced alcohol was collected for all individuals by questioning. In addition, a nested case-control study of 81 cases of OND and 136 age and sex-matched controls was performed to investigate whether syphilis or a variety of other neurological disorders were responsible for a substantial proportion of cases of OND. Our data suggest that in this population, onchocercal infection is the single most important cause of OND and may account for 50% of all cases. Some 13% of cases were associated with signs suggestive of glaucoma. DEC use might be responsible for up to 30% of all OND. We found no evidence to suggest that any of the following are important causes of OND in the communities studied: CSM, syphilis, neurological syndromes such as polyneuropathy or other generalized neurological disease, consumption of raw cassava, consumption of locally prepared alcohol. keywords optic nerve disease, onchocerciasis, risk factors, diethylcarbamazine, chloroquine, neurological disease correspondence S. N. Cousens,

Onchocerciasis as a Risk Factor for Night Blindness

“…It is notable that subjects with ocular hypertension were five times more likely to report night blindness in this study. We found no evidence to suggest that any of the following are important causes of OND in the communities studied: cerebro spinal meningitis, syphilis, neurological syndromes such as poly-neuropathy or other generalized neurological disease, consumption of raw cassava, and consumption of locally prepared alcohol 22 .…”

Blue-yellow colour vision in an onchocercal area of northern Nigeria

“…The sensitivity of the screening plates alone for probable or definite optic nerve disease (as defined in our earlier paper21 and in appendix ) in an individual was 35%, and the specificity 97%. For the grading plates, the sensitivity was 55% and the specificity 92%.…”

“…This could be due to a further increase in comprehension of the test itself in this group, or it is possible that the test is detecting preclinical optic nerve disease and those not undertaking secondary education are more at risk of this. In a case-control study, over 50% of optic nerve disease in the communities examined was estimated to be attributable to onchocercal infection 21. Those children who were working in the fields, rather than going to school, would be more at risk of onchocerciasis.…”

Presumed Onchocerciasis Chorioretinitis Spilling over into North America, Europe and Middle East

“…Ophthalmologists would like to extrapolate the results of the skin effect to the choroid in the hope of curing this cause of blindness. Cousens et al [35] in his field study in mesoendemic communities in Nigeria concluded that annual delivery of ivermectin in a sustained fashion could halt onchocercal blindness from optic atrophy. These findings were confirmed by different investigators [18,36,48].…”